1. Field of Invention
The present invention concerns improvement in liquid-liquid contactor in which two liquids are continuously contacted in counter current flow due to the density difference between the two liquids. A liquid-liquid contacting operation is one of important separation operations, and is widely used for liquid-liquid extraction, indispensable in the petroleum refinery, petrochemistry, coal chemistry, nuclear energy processing, and many other processing industries.
2. State of the Art
A variety of types of liquid-liquid contactors has been developed. Industrial contactors are consisted of two types : one is unagitated type such as perforated-plate towers, packing towers, and baffle towers; second is mechanically agited or pulsed type, such as rotary disk towers, Oldshue-Rushton towers, pulsed towers and reciprocating-plate towers.
Performances required for a liquid-liquid contactor are: (1) high throughput, (2) free from scum accumulation, (3) easy maintenance, and (4) high extraction efficiency when used for extraction.
Conventional contactors have the following disadvantages: with respect to perforated-plates, towers and packing towers used for liquid-liquid systems in which scums are produced, the towers are likely to cause plugging. Baffle towers such as disk-and-doughnut type, side-to-side type and center-to-side type have large cross-sectional areas for liquid to flow fast. Therefore, scum hardly accumulates, however, extraction efficiency is not high. Rotating disk contactors and other mechanically agitated or pulsed contactors exhibit relatively high extraction efficiencies, and are free of plugging. However, investment and maintenance costs are relatively high.